DEEP: The Future of Snow. Day 5: Stevens Pass to Bozeman

Day 5: Stevens Pass to BozemanSnow showers. High near 35. West wind 8 to 16 mph. Chance of precipitation is 100%. Total daytime snow accumulation of 1 to 3 inches possible.

The ridges around Leavenworth are hidden behind fog in the morning. We have 600 miles between us and Bozeman and a day to cover it in. The sun is shining further down Route 2 as we make our way over the eastern plains of Washington to I-90. There are orchards here and a few vineyards, a steady stream of traffic moving southwest.

• In terms of spatial extent, seasonal snow-cover is the largest single component of the cryosphere (ice, snow, glaciers, ice sheets and permafrost) and has a mean winter maximum areal extent of 47 million square kilometers, about 98 percent of which is located in the Northern Hemisphere.
• The 28-year trend in snow extent derived from visible and passive microwave satellite data indicates an annual decrease of approximately 1 to 3 percent per decade with greater deceases of approximately 3 to 5 percent during spring and summer.
• One region where the snow appears to be diminishing rapidly is the Western United States, especially in spring when the duration of snow cover has been decreasing by 2-3 days per decade.
• Precipitation in regions of seasonal snow cover appears to be constant or increasing slightly in some locations over the same time period, which suggests that diminishing snow cover is the result of increasing temperatures.
• Long-term forecasts suggest a 60-80 percent decrease in monthly maximum snow water equivalent (the amount of water that would result from snowfall) in mid-latitude regions by 2100.

Near the Idaho border, a long line of clouds moves in from the southwest. The front cuts a clear line across the sky, and I hit the gas to stay in front of it. Heavy snow is predicted in Missoula by midnight. It's 5 p.m. now and we're six hours away from it. The goal is to stay in front of the storm, sleep for a few hours in Bozeman, then ski Big Sky tomorrow.

We cruise past Coeur d'Alene and Kellog, Idaho, site of the longest single-stage gondola in the world—and the strangest ski town I've ever seen. The highway climbs over Lookout Pass and we watch the thermometer drop. There's rain coming down now. The storm is catching up. The higher we climb the lower the temperature goes until it hits 32 and the first flakes swing down out of the night and arc up and over the windshield. By the time we cross the Montana border, it's a full-on blizzard and we can't see 200 yards in front of the car.

We push through the storm for an hour and get ahead of it again. The road is dry and we can see stars. There is no moon, there are only a few trucks lumbering down the highway. In the rearview mirror, the mountain passes are blurred in white, the raging storm just a few dozen miles behind.

We stop for a late dinner at the Broken Arrow Cafe in Deer Lodge, Montana. It's a gem of a find—cowboys in 10-gallon hats, thick steaks and apple pie. We relax for an hour until the waitress comes over and asks, "You looked outside?" We tell her no, it was clear and starry when we walked in. "I ain't never seen wind and snow like that," she said walking away.

Snow is blowing sideways when we get back to the Prius. We hit the gas and try to outrun it again. The blizzard is a near whiteout in Warm Springs. A flashing sign in Butte declares a detour on I-90 for trailers, due to high winds on the pass. We should have pulled over, but a big storm means a big powder day and we were still two hours from Bozeman.

The Prius has a surprisingly good traction control feature that keeps us on the road. The forest is black and there are scattered lights on the valley floor below. The Prius charges up, and we hit a steady 75 mph at the bottom and make Bozeman by midnight.

This series follows a yearlong, global project to document disappearing snow in the Northern Hemisphere. We'll be interviewing meteorologists, scientists, skiers, farmers, and anyone who knows anything about snow along the way. The coverage started in Portland, Oregon, on a trans-Rockies road trip, and will continue across the U.S. and Europe.